This application claims priority from Japanese patent application number 11-307241, filed Oct. 28, 1999, which is hereby incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a method and apparatus for adjusting the direction of a satellite dish antenna, and a satellite receiver having a function to assist adjustment of the direction of a satellite dish antenna.
2. Description of Related Art
In order to receive a satellite broadcast signal from broadcasting satellite (BS) or communications satellite (CS), it is necessary to install a satellite receiver and a satellite dish antenna. In general, a parabolic antenna is used as the satellite dish antenna. The parabolic antenna receives a signal from a satellite, and a satellite receiver takes images and sounds from the received signal and then transfers them to an output device such as a television and a speaker.
In general, a parabolic dish antenna has very strong directivity. For this reason, when the direction of the parabolic dish antenna is displaced by approximately 2 degrees, the output to the satellite receiver is reduced to half or less. The reduction of output to the satellite receiver causes a harmful effect such as distortion of images and sounds, and in the worst case it may cause the receiver failure. Therefore, accurate adjustment of the direction of the antenna such as an elevation angle, a horizontal angle and a polarization angle is necessary. Rough adjustment of the direction is made first by using graduations provided on the antenna and then fine adjustment is made. Most of currently available satellite receivers have a function to display the intensity of a signal received by the antenna as a numerical value or a bar graph on a display screen of a television or the like. Alternatively, the intensity of a signal received by the antenna may be given as a sound volume output from a built-in speaker of the television or the like. The direction of the antenna is adjusted by using such a function of the receiver so that the signal received by the antenna can attain the maximum intensity.
FIG. 6 shows the structure of a satellite receiver 80 and an example of connection between a parabolic dish antenna 70 and an output device 76, but FIG. 6 mainly shows a part associated with the adjustment of the direction of the parabolic dish antenna 70. The parabolic dish antenna 70 is connected to the satellite receiver 80 through a connection cable 74. A coaxial cable is generally used as the connection cable 74. Between the parabolic dish antenna 70 and the connection cable 74, a low noise block converter (LNB) 72 is disposed. The LNB 72 has a function of, for example, converting a received signal having a frequency band of 10 GHZ into a signal having a band frequency of 1 GHz. The satellite receiver 80 includes a tuner 82, an automatic gain control (AGC) 84, a microprocessing unit (MPU) 86 and an output processing unit 88.
The tuner 82 tunes the television to a channel of a desired broadcast program. The 1 GHz signal received from the LNB 72 through the connection cable 74 is sent from the tuner 82 to the AGC 84. The AGC 84 generates an output in accordance with the received signal as well as stabilizes the output through gain control. The output of the AGC 84 is substantially in proportion to the intensity of a signal received by the antenna. Therefore, the output of the AGC 84 can be used as an index for adjusting the direction of the antenna 70. For example, the direction of the parabolic dish antenna 70 is adjusted so as to maximize the output of the AGC 84. The amplitude of the output of the AGC 84 can be measured with a measuring device such as a tester, which most homes do not own. Accordingly, in many cases, a numerical value corresponding to the amplitude of the output of the AGC 84 is displayed on the television screen or a sound in accordance with the amplitude of the output of the AGC 84 is output from the speaker. The output device 76 such as a television and a speaker is connected to the satellite receiver 80 through an output cable 78.
The output of the AGC 84 is input to the MPU 86. The MPU 86 outputs a received intensity signal in accordance with the output of the AGC 84. The received intensity signal used herein is obtained by converting the output of the AGC 84 into a numerical value ranging from 1 to 30. The output processing unit 88 converts the received intensity signal into an image signal or a sound signal. The image signal is output to the television screen or the like, and the sound signal is output to the speaker or the like. The image signal is used, for example, for displaying the numerical value (1 to 30) corresponding to the received intensity signal as a numerical character or a bar graph. The sound signal is used, for example, for changing the frequency or the volume of a sound to be output in accordance with the numerical value (1 to 30) corresponding to the received intensity signal. Based on the image displayed on the television screen or the sound output from the speaker, the direction of the antenna 70 is adjusted so as to maximize the intensity of the signal received by the antenna 70.
However, these adjustments are made only by peripheral equipment of the satellite receiver 80. In order to display the received intensity on the television screen, the television screen should be seen from a place where the parabolic dish antenna is installed. For example, in the case where the antenna is installed near the window of a room where the satellite receiver is placed and the television screen can be seen from the place where the antenna is installed, the direction can be easily adjusted. However, in the case where the antenna is installed, for example, on the roof, the television screen cannot be seen from the place where the antenna is installed, and therefore the direction of the antenna cannot be accurately adjusted.
In such a case, the direction is generally adjusted by two persons: one is an adjuster of the direction; and the other is an instructor for instructing the adjuster on the direction while watching the television screen. In this case, however, it is difficult to make fine and accurate adjustment of the antenna to an optimal direction. In general, an antenna is installed outdoors on the roof of a house or a building, and the satellite receiver is installed indoors near a television. Thus, in many cases a satellite receiver is away from an antenna. When the direction is thus adjusted by two persons, the adjuster sometimes cannot hear the voice of the instructor. Similarly, when the received intensity is output from the speaker, the adjuster sometimes cannot hear the output sound.
A reliable method of seeing the television screen without fails is to bring a compact television and the satellite receiver near the antenna so that the direction can be adjusted while checking the image displayed on the television screen. However, this method requires a compact television, and it is necessary to bring the compact television and the satellite receiver to the place where the antenna is installed, for example, to the roof, which entails danger. In addition, since a coaxial cable for connecting the receiver to the antenna is already. installed, an additional coaxial cable has to be prepared to be connected to the satellite receiver moved to the place for installing the antenna when the readjustment of direction of the antenna is required.
On the other hand, an expert in installing an antenna uses special equipment for measuring the intensity of the received signal. In most of such equipment, the intensity of the signal received by the antenna is displayed as a numerical value or a bar graph on the screen. This equipment is connected to the end terminal of the antenna (LNB), and the direction of the antenna is adjusted so as to maximize the intensity of the received signal measured with this equipment. Since this equipment is driven by a battery and hence is portable, it can be used in any place for adjusting the direction of the antenna. However, this equipment is quite expensive because of its specialty.
Thus, it is difficult for a general user to accurately adjust the direction of an antenna. In order to accurately adjust the direction, it is necessary to prepare or purchase special equipment necessary for the direction adjustment. In addition, when an antenna alone is purchased through mail order or the like, it is difficult for the purchaser to arrange an expert in its installation, so that the antenna should be installed by the purchaser himself/herself. Moreover, the direction of an antenna should be readjusted when, for example, the angle of the antenna is shifted due to strong wind or the like.
An object of the present invention is to inform a person who adjusts the direction of an antenna of the intensity of a signal received by the antenna without connecting or adding special equipment to the antenna or a connection cable.
The method of adjusting the direction of a satellite dish antenna according to the present invention comprises the steps of: outputting received intensity information in accordance with the. intensity of a signal received from the satellite dish antenna; superimposing the received intensity information on a carrier wave; superimposing the carrier wave carrying the received intensity information on a connection cable; and receiving the received intensity information leaked from the connection cable.
The satellite receiver of the present invention comprises: means for outputting received intensity information in accordance with the intensity of a signal received from a satellite dish antenna; means for superimposing the received intensity information on a carrier wave; and superimposing the carrier wave carrying the received intensity information on a connection cable.
The apparatus for adjusting the direction of a satellite dish antenna according to the present invention comprises: means for superimposing received intensity information in accordance with the intensity of a signal received from the satellite dish antenna on a carrier wave; and means for superimposing the carrier wave carrying the received intensity information on a connection cable.